Time For a New Furnace

[william8]

Ok Willem I understand. The variable speed blower wouldn't compensate?

If the blower can not get enough air, it will run faster. The blower will ramp up to try and force air through the small ducts, causing it to be loud and potentially "hunt" (speed up and slow down) as it can't achieve the required airflow.
And new furnaces require ECM motors. VERY expensive to replace.

 

[Chetlaham]

Chet, have you had your current furnace heat exchange inspected?? Is the rust from that?

The rust is from the evaporator coil raining down the side and interior of the furnace.

 

[Chetlaham]

He wants to increase his BTU 4x, that would require bigger ductwork:

Many houses could benefit from larger ductwork, but the cost on an existing structure is prohibitive.

My heat is already oversized by about 3-4x.

I said I like it that way, not that I want to increase my current 100,000 BTUs to 400,000 BTUs.

The AC on the other hand is to small, need a 2x from the current.

 

[vacerator]

Chet, I would keep it if it is safe to use and save the expense of a new furnace until it is shot. It will take years to recoup the energy savings over the up front cost of a new one.

 

[Chetlaham]

Is that enough? Another science denier...

Not everything is a conspiracy. Honest mistakes and ignorance are enough. Class J isn't perfect to obsessed with dancing around equilibrium even though it is born out of good intentions. But being honest I like class J. You can take the final numbers and multiply them by a good safety or comfort factor and you're all set.

 

[william8]

My heat is already oversized by about 3-4x.

I said I like it that way, not that I want to increase my current 100,000 BTUs to 400,000 BTUs.

The AC on the other hand is to small, need a 2x from the current.

You only require 25K BTU? How tiny is the house? Like I said, mines only 60K, and the return duct is much larger, so is the filter. 2000 sq ft, very cold climate. Design temp is -10f for heat

AC is 2 ton, and slightly oversized, they don't make a 1.7 ton, which is what the manual J showed. Works fine.

 

[phillymatt53]

I know there are members on here, including myself who are frequently accused of making off topic comments or veering a thread off course when the replies are not succinctly in parallel with the OP's question.

However I myself do not see oil, gravity or hot water heat as being off topic in relation to this thread. Perhaps my definition of being tangential is far more liberal than that of others. It is interesting and educational to know the life expectancy of different types of systems and their behavior in relation to forced hot air. The knowledge gained from this can help better my system, and it is comforting to know that I am not the only one experiencing hiccups despite having a different type of heating system.

Vacerator, I don't mean to raze you. You're been nice and you've always liked my posts when no one else has. I should do the right thing and reciprocate. You are a very friendly forum contributer.

Just wanting to say that I don't mind comments about oil, gravity, steam, hot water or other types of heat

When in person with several people, say, at a dinner party, it's natural to wander with topics, because sometimes things come to mind that cause another to bring up perhaps a similar subject.
It's Human Nature, not unusual or purposly disruptive.
It's the way humans are.

 

[Chetlaham]

When in person with several people, say, at a dinner party, it's natural to wander with topics, because sometimes things come to mind that cause another to bring up perhaps a similar subject.
It's Human Nature, not unusual or purposly disruptive.
It's the way humans are.

Much indeed, and what might seem tangential or off topic to some is actually interconnected with the subject matter. Just as mentioning time and mass after space was brought up 200 years ago at a university might seem widely extraneous when today we know mass, time and space all have a profound relationship with one another.

 

[william8]

Not everything is a conspiracy. Honest mistakes and ignorance are enough. Class J isn't perfect to obsessed with dancing around equilibrium even though it is born out of good intentions. But being honest I like class J. You can take the final numbers and multiply them by a good safety or comfort factor and you're all set.

More conspiracy. And it's Manual J, the questions below would answer if it was done correctly. It's not guessing, or opinion based.

So what was the static pressure on the commissioning report when they installed the furnace? What was the Delta T for AC, what was the heat rise?
Hard to offer advice when someone won't give the required information. How big is the home, what's the climate?

 

[phillymatt53]

Being overly obsessed about something that is natural for humans to do creates problems and unrest of others.
Discussions over the internet are not different from a couple of guys sitting on the back porch, talking.
In fact, if several in a group become the type to regularly criticize or put down others, they're labeled.
Yes, websites have rules, and should be respected, but nitpicking over trivial things gets boring.

 

[neptunebob]

The longest lasting furnace is a boiler

Houses with hydronic hot water heat will not need a new boiler for at least 30 years. My sister had a 90 year old house and the second boiler was installed in 1948, the previous boiler was coal and this one is gas. Not all that efficient but as of yesterday it still heated when it was cold.

So Chet, buy a house with hot water heat, start the day with a fiber drink and you will be much happier in life.

By the way, don't have too big an air conditioner if you live in a humid area, you will feel icky when the oversize machine cools the temperature down but does not take the time to remove the humidity.

 

[phillymatt53]

The longest lasting furnace is a boiler

Houses with hydronic hot water heat will not need a new boiler for at least 30 years. My sister had a 90 year old house and the second boiler was installed in 1948, the previous boiler was coal and this one is gas. Not all that efficient but as of yesterday it still heated when it was cold.

So Chet, buy a house with hot water heat, start the day with a fiber drink and you will be much happier in life.

By the way, don't have too big an air conditioner if you live in a humid area, you will feel icky when the oversize machine cools the temperature down but does not take the time to remove the humidity.

I have to say, my 2002 Crown "Aruba" gas boiler is as I mentioned previously in post #7 has been great all these years.

And the wall mounted old 1970s Westinghouse 24,000 BTU was a power-hungry animal that cooled the downstairs way too much, feeling like I walked into a WAWA store, and gave me goosebumps.
But when I ripped it out in 2005 and installed the more efficent GE 18,000 BTU, it did the job without feeling icy cold.

 

[Chetlaham]

More conspiracy. And it's Manual J, the questions below would answer if it was done correctly. It's not guessing, or opinion based.

So what was the static pressure on the commissioning report when they installed the furnace? What was the Delta T for AC, what was the heat rise?
Hard to offer advice when someone won't give the required information. How big is the home, what's the climate?

Your right, it is manual J. I called it class J without thinking.

However what you call a conspiracy I call being to liberal. I like having a safety factor to my living.

 

[pstehle]

I'm debating going back to a centra HP system. My home was moved to the lot in the 1980's, and originally had gas service. That wasn't an option in the new location, so it got a 4 ton split heat pump without backup as we don't really need it in Phoenix. We need heat a few hours in the morning for maybe two weeks, but we REALLY need a/c all summer. I switched to a total of 4 tons of mini-splits, and have been comfortable and happy enough, but looking to use the house as a rental or sell it, I think a standard system will be more attractive and simpler to maintain... The ducted system was always very loud, given that the house was built in 1966 and one or two notches above a spec build, I wonder if the original system was 80kbtu/3 ton. I've upgraded the windows to thermopane low-e argon, and plan to add maybe a foot to the blown-in fiberglass in the attic. Opinions?

 

[william8]

Your right, it is manual J. I called it class J without thinking.

However what you call a conspiracy I call being to liberal. I like having a safety factor to my living.

Ans still, not a single answer...
What is safe about a 4x oversized furnace?

 

[estesguy]

I lived in a rented twin home, that the landlord must have got a deal on a replacement furnace in the past. It was 100,000 BTU, when I'm sure a 75,000 would have been fine. The problem is with the furnace being too large overruns the thermostat, because it can't respond fast enough to shut the system down, resulting in the place getting uncomfortably warm. I found a Honeywell thermostat I could adjust the cycle times on, to cause the unit to shut down sooner, which results in a short cycling of the furnace, but I had to be able to live there. That, along with other issues, I moved out after my 1 year lease, and put the old thermostat back. I feel sorry for the people who lived there before and after me.

 

[Chetlaham]

Ans still, not a single answer...
What is safe about a 4x oversized furnace?

Why would anything be dangerous in the first place?

My furnace isn't overheating, duct work is ok, exhaust gases are within spec, high limits aren't tripping.

Most gas furnaces are over-sized by Manual J standards. And with the millions of over-sized furnaces there is no epidemic of fires, carbon monoxide, ect.

 

[william8]

Why would anything be dangerous in the first place?

My furnace isn't overheating, duct work is ok, exhaust gases are within spec, high limits aren't tripping.

Most gas furnaces are over-sized by Manual J standards. And with the millions of over-sized furnaces there is no epidemic of fires, carbon monoxide, ect.

Still no answers...I don't think your furnace is 4x oversized. Unless you have a 750 sq. ft. house.
Never said it wasn't safe. I asked what WAS safe. What does that even mean?

 

[Chetlaham]

I lived in a rented twin home, that the landlord must have got a deal on a replacement furnace in the past. It was 100,000 BTU, when I'm sure a 75,000 would have been fine. The problem is with the furnace being too large overruns the thermostat, because it can't respond fast enough to shut the system down, resulting in the place getting uncomfortably warm. I found a Honeywell thermostat I could adjust the cycle times on, to cause the unit to shut down sooner, which results in a short cycling of the furnace, but I had to be able to live there. That, along with other issues, I moved out after my 1 year lease, and put the old thermostat back. I feel sorry for the people who lived there before and after me.

I'd gladly live there as long as what you describe isn't to pronounced. Hot air leaving the register doesn't give that drafty feel while the furnace is running. Rather a nice warm breeze. Like having a fireplace at each vent. There might be a temperature over shoot but you factor that in by setting that stat 1 or two degree lower. Eventually it gets cold again and there is a call for heat.

I can not stand luke warm or warm air. The air leaving the register for me has to be HOT and it has to heat quickly. I will never take gas forced air for granted.

 

[Chetlaham]

Still no answers...I don't think your furnace is 4x oversized. Unless you have a 750 sq. ft. house.
Never said it wasn't safe. I asked what WAS safe. What does that even mean?

Even if it is 2x over sized, I like over-sized. I will never size anything to a straight manual J calculation. And I hate that this is becoming the normal vs rule of thumbs that worked for decades.